- "The Wraith allow our kind to grow in numbers, and when that number reaches a certain point they return to cull their human herd. Sometimes a few hundred years will pass before they awaken again. We've visited many, many worlds -- I know of none untouched by the Wraith." - Teyla Emmagan
The Wraith are a parasitical lifefrom in the Pegasus galaxy that feeds off of other species' genetics and biomatter. They have been the dominate race in Pegasus for the last 10,000 years since they forced the Lanteans to abandon the galaxy.
The Wraith first appeared on the remote planet, Ijara, in the Pegasus galaxy a little over 10,000 years ago. The Lanteans encountered them on the planet where they had previously placed one of thousands startup groups of the human seed species and hear the local tales of how the Wraith began on the dark side of the planet.
Because of this and other stories among the indigenous populations, the Lanteans believed that this was the homeworld of the Wraith. The Lanteans tried to convince the Wraith to stop feeding on humans, when that failed, the Lanteans grudgingly went to war to stop the slaughter. At first, the Lanteans had a tremendous advantage over the wraith. Their pesqua inflicted massive damage on the Wraith ships while their shields kept them safe. The Lanteans scored numerous victories early on, making them become even more arrogant and overconfident in the technology they had inherited from the Alterrans. Their overconfidence combined with their lack of knowledge of how to fight led them to make the mistake of sending their ships into fights alone. The Wraith managed to capture one of these vessels. The potentia was used to power Wraith cloning facilities, multiplying their numbers exponentially. With these increased numbers the Wraith started to turn the war against the Lanteans. No matter how much damage the Lanteans inflicted, there were still more Wraith in the fight. It was only a matter of time before the Wraith pushed the Lanteans back to Atlantis and bottled them up on Lantea.
After the Lanteans left, the Wraith lorded over the galaxy as boogeymen. They would feed on the humans of the galaxy until the human population shrank below the level needed to sustain the Wraith population. When that happens, the Wraith would go into hibernation for decades or centuries, until the human population has grown enough. They have been doing this for 10,000 years, until the arrival of the expedition from Avalon came to Atlantis. When, then Major, Sheppard killed a queen, all of the hibernating Wraith woke up at once. Too many Wraith with too few humans to feed off of.
In the ensuing fight with the Avalon expedition the Wraith suffered greatly. While technologically inferior to the Lanteans, the humans knew how to fight a war, and they were in possession of technology from the Asgard. As the war with the Wraith became untenable to Avalon and they began to withdraw from Pegasus, Stevenson encountered the Repository of Knowledge and took possession of Atlantis. Now the Wraith will fight the Alterrans, a far superior opponent who knows how to fight a war. Let's see how well they will do.
The Alterra have determined that the Lanteans were wrong. The Wraith did not evolve on the planet where the Lanteans found them. They were only on Ijara for a year or so before the Lanteans found them. They were created by the combination of the seed species and an unknown species thought to have originated somewhere in the vicinity of Ijara.
Wraith are bipedal creatures that feed off the life energy of other species. They are very agile and have demonstrated extraordinary strength. They lack the inhibitive proteins found in humans, giving themselves excellent regenerative abilities. If a Wriath has recently fed, they can take many times the truama a human could handle before they finally fall. If properly nourished, Wraith cells can regenerate indefinitely, giving the Wraith immortality.
The Wraith have limited telepathic abilities. They are able to transmit thoughts and images across short distances. The Wraith 'ghosts' are part of this ability. Wraith can project phantom images into their prey's minds, distracting them. While one Wraith has a short range for its telepathy, many Wraith can work together to increase their range, even reaching interstellar distances with large enough groups. This is how Wraith ships communicate, the crew can work together to get messages to other ships anywhere in the galaxy.
The scariest aspect of the Wraith is their feeding process. It scares different species for different reasons. It scares the seed species because of the pain and violation that goes with having your life force taken away. For the Alterrans, who have discovered the truth, it is far worse and much scarier. Whoever created the Wraith gave them an ability similar to adaptive genetics. The Wraith absorb other species genetics through the feeding process, incorporating their physical attributes and intelligence. It is possible that they can even absorb memories as well. During the war with the Lanteans, when the Wraith captured Lanteans and fed off them, the Wraith became much smarter and boosted their technology. Luckily, after feeding on several generations of humans, the Wraith have lost their intelligence and ability to operate the more advanced technology.
Wraith operate much like ants or other hive based insects. They have a queen which leads them and handles reproduction. There are males who are scientists and engineers, they also serve as battlefield commanders. The final caste within Wraith society is that of the warriors. These unimaginative males form the backbone of Wraith armies.